The present invention relates generally to mechanical conveyors and, more particularly, to mechanical conveyors employing a roller chain as the primary weight-bearing element.
Various types of mechanical conveyors are known in industry for transporting articles from one part of an industrial plant or warehouse to another. Especially common are conveyors for transporting goods in cartons, boxes and the like. One common type is a conveyor belt assembly wherein an endless conveyor belt travels over a bed formed of rollers positioned transversely along the path of travel of the conveyor belt. The rollers bear the weight of the transported items and provide a low-friction bed over which the conveyor belt travels along its path of travel.
Such conveyor belt assemblies are known to have certain limitations and disadvantages. For example, they are generally limited to a straight path of travel. Multiple belts and their associated drive mechanisms are required to accommodate a curved path of travel. Also, the bearing assemblies of the numerous rollers are costly, noisy, subject to wear and require periodic maintenance. Finally, the belt tends to progressively stretch and deteriorate and requires periodic adjustment to maintain the correct tension.
In other applications a bed of rollers is employed without an overlying conveyor belt. Such a bed of rollers is suitable where articles such as rigid cartons or boxes are to be transported, but is generally unsuited to conveying small or irregularly shaped articles. The rollers of such a conveyor may be independently driven or freely journalled to the conveyor frame. In the case of freely journalled rollers, the conveyor assembly must be inclined or the articles must be otherwise propelled. Where the rollers are independently driven, each roller typically includes a chain sprocket at one end. An endless roller chain connects all of the roller sprockets to a drive motor. Such assemblies are dangerous because of the numerous sprocket/chain contacts. Such assemblies are also more subject to failure because of their greater mechanical complexity.
Certain mechanical conveyors known in the art employ one or more roller chains as the primary weight-bearing elements. A recognized problem with the use of roller chains as conveyor elements is that they are unstable and are subject to lateral, vertical and torsional displacement from their normal path of travel. Accordingly, various types of guides and sprockets are used to keep the roller chain element on course. The routine use of sprockets for this purpose is undesirable from a safety standpoint because they introduce relatively dangerous sprocket/chain pinch points. The various other types of chain guides known in industry are either inefficient for stabilizing the chain against lateral, vertical and torsional displacements or they introduce unacceptable amounts of friction along the path of travel of the conveyor chain.
Another disadvantage of using roller chains as weight-bearing elements in conveyors wherein the chain slides along a supporting surface is that the chain does not have a sufficiently large bearing surface area to prevent wear and abrasion. Consequently, both the chain and the surface on which it bears undergo relatively rapid deterioration with use. Also, it is difficult to adapt such a roller chain to accommodate a predetermined curved path of travel without also introducing unacceptable levels of friction in the conveyor assembly.
Accordingly, it is an object of the present invention to provide a mechanical conveyor wherein a conveyor element includes a weight-bearing roller chain that is constrained against lateral, vertical or torsional displacement from its normal path of travel.
It is also an object of the present invention to provide a conveyor that is economical to fabricate, has fewer moving parts and is easier to maintain and clean than a conventional conveyor belt or roller bed conveyor assembly.
It is a further object of the present invention to provide a mechanical conveyor that is safer than those heretofore available by reason of having fewer pinch points and fewer exposed sprocket/chain contacts.
It is still another object of the present invention to provide a mechanical conveyor employing a roller chain conveyor element that can accommodate a curved path of travel.
It is yet another object of the present invention to provide a conveyor that can accommodate a curved path of travel with a single drive mechanism.
It is still another object of the present invention to provide a roller chain for a conveyor that can accommodate a curved path of travel and which has an improved bearing surface for reducing wear due to abrasion.